Comparative optical studies on violet InGaN quantum well laser diode structures grown on sapphire and GaN substrates

Abstract

Abstract We have investigated the optical properties of violet In x Ga 1–x N/In y Ga 1–y N multiple quantum well laser diode structures grown on sapphire and GaN substrates by means of photoluminescence (PL), PL excitation, and time‐resolved PL spectroscopy. The PL result shows a red‐shift behavior of the emissions from GaN capping layer and the 10‐nm‐thick In y Ga 1–y N barriers on the GaN substrate due to the reduction of residual compressive strain. On the other hand, we have observed a blue shift of the PL emission from the 4‐nm‐thick In x Ga 1–x N wells for the samples grown on GaN substrates. This can be attributed to the reduction of strain‐induced piezoelectric field between In x Ga 1–x N wells and In y Ga 1–y N barriers due to the direct growth on GaN substrates, which is confirmed by a reduction of the Stokes‐like shift between In x Ga 1–x N PL and its absorption edge and a decrease in overall decay lifetimes for the samples grown on GaN substrates. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)